A large proportion (some estimates are as high as twenty-five percent) of the electricity generated in the United States each year goes to lighting. It is well known that incandescent light bulbs are very energy-inefficient light sources—about ninety percent of the electricity they consume is released as heat rather than light. Fluorescent light bulbs are more efficient than incandescent light bulbs (by a factor of about 10) but are still less efficient than solid state light emitters, such as light emitting diodes (LEDs).
Although the development of light emitting diodes has in many ways revolutionized the lighting industry, some of the characteristics of light emitting diodes have presented challenges, some of which have not yet been fully met. Efforts have been ongoing to develop lighting devices that are improved, e.g., with respect to energy efficiency, color rendering index (CRI Ra), contrast, efficacy (lm/W), and/or duration of service. In addition, efforts have been ongoing to develop lighting devices that include solid state light emitters instead of other forms of light emitters. Ideally, the cost of such lighting devices should be comparable with traditional incandescent lighting to facilitate their acceptance and utilization.
Many modern lighting applications utilize high power solid state emitters to provide a desired level of brightness, which can draw large currents, thereby generating significant amounts of heat that must be dissipated to maintain the output of the solid state emitters. Many solid state lighting systems utilize heatsinks in thermal communication with the heat-generating solid state light sources, whereas heatsinks of substantial size and/or subject to exposure to a surrounding environment, aluminum is commonly employed by forming in various shapes by casting, extrusion, and/or machining techniques. Leadframe-based solid state emitter packages also utilize chip-scale heatsinks, with such heatsinks and/or leadframes being fabricated by techniques including stamping with such chip-scale heatsinks typically being arranged along a single non-emitting (e.g., lower) package surface to promote thermal conduction to a surface on which the package is mounted. Such chip-scale heatsinks are generally used as intermediate heat spreaders to conduct heat to other device-scale heat dissipation structures, such as cast or machined heatsinks.